The present invention relates to a traffic light backup system using light-emitting diodes (LEDs). Such a system allows traffic lights to function even though there might be a power failure.
The high prevalence of traffic lights for controlling the traffic flow attest to their effectiveness in reducing the incidence of accidents and, more recently, their utility in controlling the flow of traffic in large metropolitan areas when used in conjunction with computer control systems. Modern traffic lights are very similar to those used in the early 1900s. The basic traffic light still employs red, yellow and green filters over incandescent bulbs that are sequentially turned on and off by an electromechanical timing switch or by solid state controllers. Each bulb is electrically coupled to a conventional power source, such as the conventional power distribution network.
One of the main drawbacks associated with the use of conventional traffic lights arises in situations when the source of electrical energy to the bulbs is cut off, such as in the event of a power failure. The use of conventional traffic lights has become so widespread and embedded in present day transportation culture that such a situation often creates traffic chaos, and may provoke potentially dangerous situations. This problem has been recognized in at least two prior patents.
U.S. Pat. No. 5,010,336 to Mosele et al. discloses an auxiliary traffic light system including a strobe light connected to a battery operated circuit for flashing the strobe upon failure of the power source supplying the conventional traffic light.
U.S. Pat. No. 5,327,123 to Heinman et al. discloses a traffic control system including a light flasher structure connected to a controller. The controller is also electrically coupled to load switches for controlling the normal operation of the lights, and flashing at least one of the lights in the event of a system malfunction.
Although offering a partial solution to the problem of inexistence of traffic control in the event of a power failure, the previous systems are overly complex, have relatively low life cycle expectancy and have low visual efficiency. The latter problem is particularly evident in the case of a power failure in daytime, when the backup lights do not have enough power to be visible.
There thus exists a need for a traffic light backup system which minimizes power requirements, has a high luminous efficiency and is easier to install than the prior art devices.
It is an object of the invention to provide a traffic light backup system which minimizes power requirements and has a high luminous efficiency. In accordance with the invention, this object is achieved with a traffic light backup system for use with a traffic light, the traffic light comprising at least one enclosure housing a bulb, said traffic light having a primary lead for each of said at least one enclosure and a neutral lead, said bulb being electrically connected to the corresponding primary lead and the neutral lead, the traffic light backup system comprising an auxiliary light associated with at least one of said at least one enclosure; rechargeable backup power means associated with said auxiliary light; at least one primary power supply and power failure detection circuit, for providing power to said rechargeable backup power means during normal operating condition and for sensing a voltage across said bulb of said at least one enclosure and providing an output related to said voltage; and an electronic control module operatively connected to said auxiliary light, said rechargeable backup power means and said primary power supply and power failure detection circuit, for receiving power from said primary power supply and power failure detection circuit during normal operating condition in order to recharge said rechargeable backup power means, for receiving said output related to said voltage and for activating said auxiliary with said rechargeable backup power means when said electronic control module determines that a power failure has occurred.
In a preferred embodiment, the auxiliary light consists of a plurality of LEDs arranged in an octagonal shape on the inside of the enclosure.
Other objects and advantages will become apparent throughout the present description.